Catheter-based Raman spectroscopy has been previously proposed for the chemical analysis and diagnosis of vascular tissue including human atherosclerotic lesions. However, typical methods of collecting Raman scattered light from the surfaces of artery do not register information about the distance of the scattering element from the collection optics. Raman spectroscopy techniques that do incorporate optical methodologies for depth-sensing information have been too large to be incorporated into intravascular catheters. One method previously explored by one of the inventors (Brennan) involved a combination IVUS/Raman catheter for intravascular diagnosis. These prior studies focused on using the Raman-scattered light in the Raman “fingerprint” region to supplement the IVUS data. The collection of Raman spectra in the fingerprint (FP) region, i.e., approximately 200 to 2,000 cm−1, through optical fibers is complicated by Raman signal from the fibers themselves. In order to collect uncorrupted FP spectra, it has been necessary to incorporate complex optics and filters on the tips of catheters and often these designs require the use of multiple optical fibers. Since the Raman-scattered signal is weak, large multimode fibers are utilized in the multi-fiber catheter designs resulting in an unwieldy catheter that is generally incapable of exploring delicate arteries, such as the human coronary arteries.
U.S. Pat. No. 5,953,477 discloses methods and apparatuses for the manipulation and management of fiber optic light, and is incorporated by reference herein in its entirety.
U.S. Pat. No. 6,144,791 discloses the use of beam steering techniques in optical probes, and is incorporated by reference herein in its entirety.
U.S. Pat. No. 6,222,970 discloses methods and apparatuses for filtering optical fibers and applying filters to optical fibers, and is incorporated by reference herein in its entirety.
U.S. Pat. No. 6,445,939 discloses ultra-small optical probes, imaging optics and methods of using the same, and is incorporated by reference herein in its entirety.
U.S. Pat. No. 6,507,747 discloses optical imaging probes that include a spectroscopic imaging element and an optical coherence tomography imaging element, and is incorporated by reference herein in its entirety.
U.S. Pat. No. 6,904,199 discloses optical catheters that include a double clad optical fiber, and is incorporated by reference herein in its entirety.
U.S. Pat. No. 7,177,491 discloses optical fiber-based optical low coherence tomography, and is incorporated by reference herein in its entirety.
U.S. Pat. No. 7,190,464 discloses low coherence interferometry for the detection and characterization of atherosclerotic vascular tissue, and is incorporated by reference herein in its entirety.
U.S. Publication No. 2001/0047137 discloses the use of near-infrared spectroscopy for the characterization of vascular tissue and teaches against the use of Raman spectroscopy for such characterization, and is incorporated by reference herein in its entirety.
U.S. Publication No. 2004/0260182 discloses intraluminal spectroscope devices with wall-contacting probes, and is incorporated by reference herein in its entirety.
U.S. Publication No. 2005/0054934 discloses an optical catheter with dual-stage beam redirector, and is incorporated by reference herein in its entirety.
U.S. Publication No. 2006/0139633 discloses the use of high wavenumber Raman spectroscopy for the characterization of tissue, and is incorporated by reference herein in its entirety. Santos et al., Fiber-Optic Probes for In Vivo Raman Spectroscopy in the High-Wavenumber Region, Anal. Chem. 2005, 77, 6747-6752 discloses probe designs for high wavenumber Raman spectroscopy, and is incorporated by reference herein in its entirety.
U.S. Publication No. 2007/0076212 discloses catheter-based methods and apparatuses for analyzing vascular tissue that combine infrared spectroscopy for chemical analysis with optical coherence tomography, and is incorporated by reference herein in its entirety.
U.S. Publication No. 2004/0260182 discloses intraluminal spectroscope devices with wall-contacting probes, and is incorporated by reference herein in its entirety.
U.S. Publication No. 2005/0054934 discloses an optical catheter with dual-stage beam redirector, and is incorporated by reference herein in its entirety.
In view of the above, what is needed is a single optical fiber-based optical probe design that enables catheter-based Raman spectroscopy and optical coherence tomography and methods of diagnosing tissue using the same.